The U.S. Geological Survey Climate Geo Data Portal: An Integrated 

Broker for Climate and Geospatial Data

Introduction

The increasing availability of downscaled climate 

projections and other data products that summarize or predict 

climate conditions, is making climate data use more common 

in research and management. Scientists and decisionmakers 

often need to construct ensembles and compare climate hindcasts and future projections for particular spatial areas. These 

tasks generally require an investigator to procure all datasets 

of interest en masse, integrate the various data formats and 

representations into commonly accessible and comparable 

formats, and then extract the subsets of the datasets that are 

actually of interest. This process can be challenging and time 

intensive due to data-transfer, -storage, and(or) -processing 

limits, or unfamiliarity with methods of accessing climate 

data. Data management for modeling and assessing the 

impacts of future climate conditions is also becoming increasingly expensive due to the size of the datasets. The Climate 

Geo Data Portal (http://cida.usgs.gov/climate/gdp/) addresses 

these limitations, making access to numerous climate datasets 

for particular areas of interest a simple and efficient task. 

The portal allows a user to process data by:

1. selecting areas of interest by uploading a polygon 

shapefile or drawing on a map, 

2. choosing from a searchable list of historical and 

future climate datasets,

3. selecting the variables and time period of interest 

from the dataset, and 

4. configuring processing to return raw data or spatially 

averaged summaries.

Datasets available in the portal are hosted by the 

U.S. Geological Survey (USGS) or outside partners using standard data distribution protocols. These protocols and the high 

bandwidth connectivity of Geo Data Portal processing servers 

eliminate the need for users to download and manage large collections of data. The Geo Data Portal processing servers act as a data 

broker, conducting all integration and subsetting automatically, 

thus removing the need for computing hardware, software, and 

expertise generally required for these data processing tasks.

A B

C

Time

Spatial average

0

2

4

6

8

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12

Monthly precipitation

1960 1970 1980 1990 2000

Figure 1. Schematic representation of Climate Geo Data Portal functions using the Mobile Bay watershed as an example of: A, grid of 

regional climate data with watershed polygons; B, subsets of regional grids for a specified time period as output by OPeNDAP Subset 

algorithm; C, gridded time series spatially averaged for a subwatershed as output by Area Grid Statistics (Weighted) algorithm.

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2013–3019

May 2013
Algorithms

The Climate Geo Data Portal offers two processing 

algorithms for accessing regional or national scale gridded 

time-series data (fig. 1A). Area Grid Statistics (Weighted)

attributes spatial statistics of gridded time-series datasets to 

any polygon or set of polygons. OPeNDAP Subset provides 

a subset of raw data for the area and time period specified. 

A user interface to interact with these algorithms is available 

at http://cida.usgs.gov/climate/gdp/.

Area Grid Statistics (Weighted)

The Area Grid Statistics (Weighted) algorithm is the 

primary processing tool made available by the Climate Geo 

Data Portal. The algorithm calculates the mean, minimum, 

maximum, standard deviation, count, and sum of contributing 

cell weights of a gridded dataset for polygons in any commonly used coordinate reference system. Spatial statistics are 

calculated using an area weighted method where the fraction of 

a grid cell actually intersecting a polygon is used to weight the 

contribution from that cell. This is best illustrated by contrasting 

the count and sum of weights statistics returned by the algorithm. Count is the total number of cells sampled to construct 

the statistics for a given polygon. Sum of weights is the sum of 

grid cell weights, or the fractional number of cells, contributing 

to the statistics for a given polygon. 

One time series of statistics is returned for each polygon 

selected from an uploaded shapefile. The coordinate reference 

system of the polygons provided, as opposed to the gridded climate data, is used for spatial intersection calculations. Outputs 

of these calculations are returned in a simple delimited text 

format to be plotted, used in a model, or applied to an analysis 

of climate. Figure 1C shows a schematic representation of this 

functionality in which a time series for a particular polygon is 

plotted to look at trend.

OPeNDAP Subset

The standard data transfer protocol used by the Climate 

Geo Data Portal to access gridded data is called the Opensource 

Protocol for a Network Data Access Protocol (OPeNDAP). 

This algorithm constructs a file containing a subset of a selected 

climate dataset derived from the larger (national, regional, etc.) 

dataset distributed using the OPeNDAP protocol (fig. 1B).

The OPeNDAP subset algorithm writes data into a 

format known as Network Common Data Format Version 3 

(NetCDF3). This format is compatible with a wide array of 

geospatial and climate data access and manipulation software, 

but has some limitations. The technical details (and limitations) 

are beyond the scope of this document. For more detail, see 

Blodgett, 2011 and documentation available on the portal.

Newly Introduced Datasets

It is important to note that the Climate Geo Data Portal is 

not limited to the datasets available from its built-in catalog. 

The address of a compatible data service can be given to the 

portal and it will work with the newly introduced dataset. 

Example Uses

The potential uses of the Climate Geo Data Portal 

described below illustrate how it can assist scientific research 

and resource management.

Hydrologic Modeling

Interest in the impacts of future climate conditions on 

water resources is growing. Spatially continuous representations of historical climate time-series datasets are required for 

calibrating hydrologic models. After calibration, climate projections can be applied to the model, and model outputs like soil 

moisture and streamflow can be produced for projected future 

conditions. The portal can be used to assist in generating time 

series of climate data, past and future, attributed to watershed 

polygons or other hydrologic modeling units.

Ecosystem Response to Changes in Climate 

Understanding how ecosystems respond to changing climate conditions is one of the largest areas of study for ecosystem management and restoration. A scientist may have a set of 

field observations to be correlated with climate data and derived 

climate indices. The scientist can use the portal to access archives 

of climate data for the area near observation sites or for an 

ecoregion of interest, and can then use the historical climate data 

to construct correlations and models of ecosystem response. Thus 

climate projections can be accessed and used to make predictions 

about future climate impacts on a given ecosystem.

Regional Adaptation Planning

Investigators can use the portal to access any data 

published via common open standards. For example, scientists 

and decisionmakers may be interested in assessing the range 

of possible climate impacts on drinking water supply or 

stormwater management infrastructure. The portal can be used 

to gain access to a particular subset of projections from many 

scenarios and projection techniques. By accessing such subsets, 

scientists and decisionmakers can form projection ensembles 

tailored for their municipalities or other areas by using the 

portal’s area grid statistics. Customized projections can assist in 

understanding the range of predictions of future climate conditions for adaptation planning.

Reference

Blodgett, D.L., Booth, N.L., Kunicki, T.C., Walker, J.L., 

and Viger, R.J., 2011, Description and testing of the 

Geo Data Portal: Data integration framework and Web 

processing services for environmental science collaboration: 

U.S. Geological Survey Open-File Report 2011–1157, 9 p.

For more information contact:

David L. Blodgett

USGS Center for Integrated Data Analytics

8505 Research Way

Middleton, WI 53562

Phone: 608-821-3899

email: dblodgett@usgs.gov